Ceramic material based on bismuth niobate substituted with zinc

ABSTRACT

The invention relates to ceramic materials based on bismuth niobate substituted with zinc and can be used for producing multilayer high frequency thermostable ceramic condensers provided with electrodes based on an alloy which comprises Ag and Pd, and also for producing multilayer microwave films. The aim of the invention is to develop a ceramic material having a low sintering temperature sufficient for using silver-vanadium electrodes having a silver content of up to 90%. Said material has an optimum dielectric permeability and thermostability which are sufficient for producing a wide range of items based on said material. Zinc niobate ZnNb2O6 having a structure of columbite with a quantity ranging from 7.0 to 99.0, expressed in mass %, is added into a ceramic material based on the bismuth niobate substituted with zinc having a crystal-chemical formula (Bi⅔[ ]⅓)2(Zn&lt;2+&gt;⅓Nd ⅔)2O6 [ ]1, [ ] being a vacancy with a pyrochlore structure. Glass having the following component ratio, in mass %, can be added into the material: PbO ranging from 26 to 33, Bi2 ranging from 14 to 24, B2O3 ranging from 4 to 10, TiO2 ranging from 15 to 21, ZnO ranging from 21 to 28.

FIELD OF THE INVENTION

[0001] The invention relates to ceramic materials based on bismuthniobate substituted with zinc and can be used for producing multilayerhigh frequency thermostable ceramic condensers provided with electrodesbased on an alloy which comprises Ag and Pd, and also for producingmultilayer microwave filters.

BACKGROUND OF THE INVENTION

[0002] In production of condensers high frequency ceramic materials withsintering temperature not in excess of 1120° C. are applied, which makesit possible to use an Ag—Pd alloy, containing no more than 30% of Pd asinner electrodes of monolithic condensers. A set of modern requirementsto radio electronic equipment makes high demands of such characteristicsof ceramic materials as dielectric permeability which must provide theproduction of the whole range of rated values of ceramic condensers,including the low capacitance range which is possible only when thelevel of dielectric permeability does not exceed 40, the temperaturecoefficient of dielectric permeability and the tangent of the angle ofdielectric losses (tg δ) or the factor of merit (Q˜1/tg δ). The latterparameter is especially important for microwave filters.

[0003] A ceramic material for high frequency condensers is known with atemperature coefficient of capacitance within the range from −3010⁻⁶deg.⁻¹ to +30·10⁻⁶ deg.⁻¹, which contains a solid solution withformula (Ba_(0,9) Sr_(0,1)) (Nd_(0,8) Bi_(0,2))₂. Ti₄ O₁₂ and glassforming compound of borosilicate xB₂O₃.ySiO₂ used as an additive (seepatent RU N 2035778, H 01 G 4/12).

[0004] Disadvantages of this material are high dielectric permeabilitywhich makes it impossible to produce on its base low capacitancemultilayer ceramic condensers (several picofarads) and not low enoughsintering temperature which prevents from using alloys with Pd contentbelow 30% as electrodes for muitilayer condensers and filters.

[0005] Bismuth niobate substituted with magnesium, zinc and nickel areknown with crystal chemical formula (Bi_(2/3)[ ]_(1/3))₂(Zn²⁺_(1/3)Nd_(2/3))₂O₆)[ ]₁, where [ ] —a vacancy as high frequencycondenser materials with high dielectric permeability (∈=145-148) at atemperature coefficient of dielectric permeability corresponding togroups M330 and M470 of thermostability and a low value of tangent ofthe angle of dielectric losses tg δ=(2-3)·10⁻⁴ (see patent RU N2021207,C 01 G 33/00).

[0006] This technical solution is selected as a prototype of thisinvention.

[0007] Disadvantages of the prototype that make it impossible to solveour problem is relatively high sintering temperature which makes itnecessary to use more expensive electrodes and low thermostability whichprevents production of thermostable ceramic condensers and microwavefilters on the base of this material.

DISCLOSURE OF THE INVENTION

[0008] The aim of the invention is to develop a ceramic material havinga low sintering temperature sufficient for using silver-vanadiumelectrodes having a silver content of up to 90 %. The said material hasan optimum dielectric permeability and thermostability which aresufficient for producing a wide range of items based on said material.

[0009] According to the invention ceramic material based on bismuthniobate substituted with zinc having a crystal-chemical formula(Bi_(2/3)[ ]_(1/3))₂(Zn²⁺ _(1/3)Nb_(2/3))₂O₆[ ]₁ with a pyrochlorestructure is characterized that zinc niobate ZnNb₂O₆ having a structureof columbite with a quantity ranging from 7.0 to 99.0, expressed in mass% is added to the said material. Glass having the following componentratio, in mass %, can be added into the material: PbO ranging from 26 to33, Bi₂O₃ ranging from 14 to 24, B₂O₃- 4-10, TiO₂ ranging from 15 to 21,ZnO ranging from 21 to 28 in the amount of 0.1-5.0 mass %.

[0010] The Applicant did not find any sources that contain theinformation on similar technical solutions, which allows, in theApplicant's opinion, to make a conclusion that the invention meets the“Novelty” criterion (N).

[0011] By implementation of the distinguishing features of the invention(in combination with the features indicated in the restrictive part offormula of invention) new important properties of the subject arereached. In the technical solution proposed high values of all basictechnical characteristics that determine the fitness of the material forusing it in production of multi-layer high frequency condensers andfilters are reached, that is sintering temperature, optimal dielectricpermeability and high thermostability.

[0012] The Applicant did not find any information on the influence ofthe distinguishing features of the invention on the technical resultobtained. This allows to make a conclusion that the technical solutionapplied conforms to the “Invention standard” criterion (IS).

BRIEF DESCRIPTION OF DRAWINGS

[0013] Further the invention is explained by detailed description ofexamples of its implementation without any references to drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The technique of producing the compound proposed is as follows.First niobate substituted with zinc with a pyrochlore structure issynthesized, next zinc niobate with a structure of columbite issynthesized. The components thus obtained are mixed and wet grindedglass is added, next it is dried and the invented material is obtained.

[0015] For the examples of synthesis of the invented compound see table1.

[0016] For main technical characteristic of specimens of the materialsobtained see table 2.

[0017] The analysis of the results shows that wide application of zincniobate makes it possible to expand the series of new materials in awide range of thermostable, and thermocompensating groups, ensures thepossibility to produce a wide range of ceramic condensers, including thecondensers belonging to the most advanced M

O group with electrodes containing not less than 30% of Pd and ensuresthe production of low capacitance thermostable ceramic condensers andthermostable microwave filters.

[0018] Specimens 1 through 8 correspond to thermostability groups

100,

33, M

O, M47 and M75, specimens 9 through 11—to thermocompensating groupsM150, M220 and M330 in accordance to OST 110309-86 “Ceramic materialsfor development of electronic equipment. Specifications.”.

[0019] Addition of glass of the said composition (RU, C1, 2035780) intothe invented material ensures additional reduction of sinteringtemperature its range being widened, results in some decrease ofthermostable and thermocompensating properties (in terms of the absolutevalue) and dielectric losses, improves technological properties of thematerial which is very important in production of multiplayer condensersand filters.

INDUSTRIAL APPLICABILITY.

[0020] The proposed material can be obtained by industrial method withapplication of widespread materials, known techniques and technical aidswhich stipulates in the Author's opinion the conformity of the inventionto the “Industrial applicability” criterion (IA). TABLE 1 Chemicalcomposition, weight, % Bismuth niobate Zinc niobate Specimen Nosubstituted with zinc ZnNb₂O₆ Glass 1 1.0 99.0 0.2 2 10.0 90.0 0.1 315.0 85.0 — 4 15.0 85.0 2.0 5 17.5 82.5 5.0 6 20.0 80.0 1.0 7 26.0 74.03.0 8 37.5 62.5 0.5 9 50.0 50.0 0.2 10 62.5 37.5 2.0 11 93.0 7.0 4.0

[0021] TABLE 2 Temperature coefficient of Sintering Tangent of angle ofdielectric temperature dielectric losses, Specimen Dielectricpermeability, (Tsn), tgδ × 10⁴ at f = 1 MHz No permeability TCE.10⁰deg⁻¹ ° C. 25° C. 125° C. 1 22 . . . 23 +118 . . . +135 1040 . . . 10600.2 . . . 1.5 0.4 . . . 3.0 2 27 . . . 29 +74 . . . +86 1020 . . . 10600.5 . . . 1.0 0.8 . . . 1.6 3 30 . . . 32 +44 . . . +50 1000 . . . 10600.6 . . . 1.2 0.8 . . . 1.6 4 29 . . . 31 +32 . . . +38  980 . . . 10400.4 . . . 0.7 0.6 . . . 1.0 5 31 . . . 33 −12 . . . +7   960 . . . 10600.2 . . . 0.4 0.3 . . . 0.8 6 32 . . . 34  0 . . . +10  980 . . . 10400.4 . . . 0.6 0.5 . . . 0.8 7 35 . . . 37 −22 . . . −24  960 . . . 10600.1 . . . 0.5 0.2 . . . 1.0 8 41 . . . 43 −73 . . . −80 1020 . . . 10600.5 . . . 0.1 0.9 . . . 1.7 9 81 . . . 84 −144 . . . −162 1020 . . .1060 1.2 . . . 1.5 1.2 . . . 2.0 10  98 . . . 101 −215 . . . −240  980 .. . 1060 1.1 . . . 1.5 2.0 . . . 2.5 11 132 . . . 140 −315 . . . −350 980 . . . 1040 0.6 . . . 2.0 2.0 . . . 3.0

1. Ceramic material based on bismuth niobate substituted with zinchaving a crystal-chemical formula (Bi_(2/3)[ ]_(1/3))₂(Zn²⁺_(1/3)Nb_(2/3))₂O₆[ ]₁ with a pyrochlore, structure is characterizedthat zinc niobate ZnNb₂O₆ having a structure of columbite with aquantity ranging from 7.0 to 99.0, expressed in mass % is added to thesaid material.
 2. The material as in p.1 is characterized that glasshaving the following component ratio, in mass %, is added into thematerial: PbO ranging from 26 to 33, Bi₂O₃ ranging from 14 to 24,B₂O₃-4-10, TiO₂ ranging from 15 to 21, ZnO ranging from 21 to 28 in theamount of 0.1-5.0 mass %.